Year	% of total fuel combustion
1971	3.556386405099214
1972	3.5142272959618337
1973	3.416803635308905
1974	3.5451197053407006
1975	3.747882937844876
1976	3.678889854924223
1977	3.515911125579881
1978	3.4383077652529024
1979	3.6049908616000117
1980	3.689392995138975
1981	3.468654002452026
1982	3.6014110312012906
1983	3.5307200444815123
1984	3.4988620472181853
1985	3.9368687211973734
1986	3.5711950623095734
1987	3.7861859132169324
1988	3.8406406010577827
1989	3.608567067353558
1990	3.3247092390647297
1991	3.194250349371132
1992	3.270124729599116
1993	3.385238836212204
1994	3.678185287258851
1995	3.4825664933480804
1996	3.505888531222345
1997	3.4720067176575817
1998	3.0184406624946245
1999	3.23515595224378
2000	3.0953272300309704
2001	3.2144885039450153
2002	3.153153153153153
2003	3.275430529108008
2004	3.4297285325571094
2005	3.44938477676623
2006	3.2513522397872276
2007	3.194839716271074
2008	3.465636746094692
2009	3.622167098883752
2010	3.367428575206787
2011	3.190101237345332
2012	3.267893104683775
2013	3.1793039306867685
2014	3.4349237319266046